Fix the defect that Heap_1.c may waste first portBYTE_ALIGNMENT bytes of ucHeap[] (FreeRTOS#238)

* Fix the defect that Heap_1.c may waste first 8 bytes of ucHeap[]

* Fix the same byte waste issue in heap_2

Author: qikai

portable/MemMang/heap_1.c

@@ -96,7 +96,7 @@ void * pvPortMalloc( size_t xWantedSize )
         if( pucAlignedHeap == NULL )
         {
             /* Ensure the heap starts on a correctly aligned boundary. */
-            pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
+            pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT - 1 ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
         }
 
         /* Check there is enough room left for the allocation and. */

portable/MemMang/heap_2.c

@@ -266,7 +266,7 @@ static void prvHeapInit( void )
     uint8_t * pucAlignedHeap;
 
     /* Ensure the heap starts on a correctly aligned boundary. */
-    pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
+    pucAlignedHeap = ( uint8_t * ) ( ( ( portPOINTER_SIZE_TYPE ) & ucHeap[ portBYTE_ALIGNMENT - 1 ] ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
 
     /* xStart is used to hold a pointer to the first item in the list of free
      * blocks.  The void cast is used to prevent compiler warnings. */